1. Field of the Invention
The present invention relates to a heat accumulator for vehicle use. More particularly, the present invention relates to a heat accumulator, for vehicle use, the vibration resistance of which is enhanced.
2. Description of the Related Art
It is common to arrange an insulated tank-shaped heat accumulator, in which cooling water is stored, in a cooling water circuit so that cooling water at a high temperature, flowing out from a water-cooled internal combustion engine, can be introduced to the engine in the case of restarting the engine for the object of facilitating the warming-up of the engine. The heat accumulator is composed of an outer tank and inner tank. When a space formed between the outer tank and the inner tank is maintained as a vacuum, cooling water in the inner tank can be effectively heat-insulated. In order to conduct heat insulation more effectively, it is preferable that the contact area between the inner tank and the outer tank is as small as possible. Therefore, conventionally, the outer tank and the inner tank are connected with each other substantially only at a joining portion where the entire periphery of an opening of the outer tank and that of an opening of the inner tank are joined to each other.
In this connection, for example, the heat accumulator is attached at a side of the outer tank of the heat accumulator to a side member of a vehicle via a bracket by a cantilever system or a hanging system. Therefore, vibration generated while the vehicle is running is relatively easily transmitted to the heat accumulator via the side member and bracket. As a result, the inner tank vibrates inside the outer tank, and tensile stress is repeatedly generated in the joint portion between the tanks. Accordingly, fatigue failure starts at this joint portion and the cooling water leaks out from the inner tank. In other words, there is a possibility that the heat accumulator is damaged.